Method for recovering valuable materials from spent catalysts



sulfides of metals of the VI Patented Apr. 18, 1933 UNITED STATES PATENT OFFICE BHEA N. WATTS, OI BATON ROUGE, LOUISIANA, ABSIGHOB T0 STANDARD-I. G.

KEG-HOD FOB VALUA'BLE IATERIALS 130E SPENT CATALYSTS Ilo Drawing.

This invention relates to the recovery of valuable materials from spent or used catalysts and more particularlly comprises a method for recovering cata ytically active oup of the periodic system, such as'molyb enum, tungsten and chromium from spent catalytic mixtures used in the hydrogenation of earbonaceous material.

In the hydrogenation of carbonaceous material under high pressure and at elevated temperature the sulfides of metals of the II, IV and VI groups of the periodic system, either alone or in combination, have been found useful as catalytic materials. The sulfides of molybdenum, tungsten and chromium preferably admixed with the sulfides of zinc and magnesium are particularly effective.

It is known that certain sulfides of these metals are more catalytically active than others, and it has been found that by heating'the oxides or other compounds of these metals in the presence of hydrogen and sulfur-containing materials for a period varying from about to 400 hours these compounds can be substantially completely converted to the active sulfides. For reasons little understood at the present time, the activity of these sulfided catalysts gradually decreases with use, and it becomes necessary to reclaim and reactivate the valuable constituents.

In a previous application Serial No. 483,- 140 filed September 19, 1930, I have described a method for the recovery of molybdenum, tungsten and chromium from spent catalytic mixtures. By that method, however, these metals are recovered as the oxides, and they must therefore be subjected to a long period of activation with hydrogen and sulfur before they are again converted to the catalyticall active sulfides.

I have now found that it is ossible to recover these valuable materia directly in the form of the active sulfides, thus eliminating the long activation period. This improved method of recove will be fully understood from the following descrlption.

The spent catalyst is first treated with a Application filed April 11,

vmay be used. It is prefera 1931. Serial No. 529,553.

chloric acid insoluble material present, such as an inert supporting material, alumina, silica, activated charcoal, and the like. In general however, the catalytic mixtures comprise the sulfides of molybdenum, chromium or tungsten, in combination with zinc or magnesium sulfides, and these latter sul fides are soluble in strong hydrochloric acid.

It is preferable to remove the hydrogen sulfide formed in this digestion with hydrochloric acid because it may convert the active VI group sulfide into a finely divided form unsuited for re-use. The hydrogen sulfide may be blown out with inert gases, or may be oxidized by an acid oxidizing agent, such as nitric acid, potassium permanganate and the like which may be added in small quantities.

The digestion with hydrochloric acid is continued until no further solution appears to take place and the undissolved active sulfide, or active sulfide and inert materials if such are present, are separated from the liquid by any suitable means, such as filtering, settling and decanting or centrifuging. The residue contains substantiall sulfide originally present. mall quantities of impurities such as oxides of iron and the like may be present in it, but these may be removed by treatment with a dilute mineral acid, say a 1 to 2 normal solution of hydrochloric, nitric or sulfuric acids. The purified sulfide may then be washed with water and dried. In the digestion of the spent catalyst with hydrochloric acid, some molybdenum may be dissolved. In this event the molybdenum so dissolved may be recovered all the active converted to the active sulfide.

The recovered e uivalent in activ ty to the freshly activated catalyst which has been subjected to a rolonged treatment with hydrogen and sul- 111 containin compounds. In some cases iii the activity 0 the recovered product is enperior to that of the original active sulfide. It may be used directly in the hydrogenation without preliminary treatment.

The recovered sulfides may be mixed with other materials such as zinc or magnesium oxides, inert supporting materials, preferably those soluble in hydrochloric acid and the mixtures used in the form of finely divided particles suspended in the oily material to be hydrogenated, or molded into small lumps of spherical, cubical, cylindrical or other convenient shapes and the lumps supgorted on trays or by other means in the ydrogenation reactor.

As an example, a spent catalyst containing the sulfides of molybdenum, zinc an 'magnesium is treated with carbon disulfide to remove hydrocarbon material, and is then digested at room temperature with 6 normal hydrochloric acid containing a small amount of nitric acid. The undissolved residue is filtered 0d, and is washed first with dilute hydrochloric acid and then with water. After drying, the recovered sulfide is mixed with magnesium oxide in the proportion of about parts recovered molybdenum sulfide to 20 parts magnesium oxide, the mixture is moistened and compressed into small lumps in a hydraulic press.

A. comparison of the activity of the cata- 1 st containin recovered molybdenum suldo with anot er catalyst containing about 50 parts fresh molybdenum oxide, 30 parts zinc oxide, and 20 parts magnesium oxide follows:

Each catalyst is used under identical conditions of temperature, pressure, feed rate, and hydrogen rate in the hydro enation of a rerun Mid-Continent gas oil, aving the following inspection:

Gravity A. P. I 40. 2 Initial boiling pt 218 l Final boiling pt 606 F. Sulfur- .221% Aniline oint 145 F. Color obinson) 19% roduct is substantially burnin distillate obtained from each reactor after a cut 2, 0 and 9 days of operation respectively are as follows:

Fresh mclybde- Recovered molybnum denum Viscosity 11.0. 40c 416 890' no These results indicate not only that the catalyst containing the recovered molybdenum sulfide is active from the beginning but that its activity is even greater than the ultimate activit oi the catalyst containing the fresh molyb enum. Thus for example after only 2 days operation the recovered molybdenum sulnde shows the same activity that it does on the 9th day, while the fresh molybdemum on the 2nd day is very much less active and does not reach its ultimate activity until about the 9th day. it should be under stood that the fresh catalyst is activated by the hydrogenation treatment itself, the sulfur in the ydrccarbon oil being suficient to dg accom lish this, although additional suliur or sul' ur-containing material may be mixed with the oil it necessary.

It is generally true that the higher the viscosity and A. P. l. gravity of a water white distillate the better are its burning gualities. It will be observed from the above ata that the distillate produced in the reactor containing the recovered molybdenum catalyst has consistently higher gravities and the same or higher viscosities than that produced with the fresh molybdenum. In this respect, too, the recovered molybdenum is shown to be superior to the fresh molybdenum. A catalyst containing mol bdenum sulfide recovered by the method escribed should therefore be particularly edicient and efi'ective in the production of water white burning distillate by hydro enation.

My invention is not limite by any theory of the mechanism of catalysis nor by any details which may have been "ven for illustrative purposes only, but is limited only by the following claims in which I wish to claim all novelty inherent in the invention.

1 claim:

1. Method for recovering sulfides of metals oi the VI group of the periodic system in a catalytically active form from. spent catalytic material containing these sulfides and the sulfides of metals of the Ill and IV groups of the periodic system and other hydrochloric acid soluble materials, which comprises digesting the spent catalyst with strong hydrochloric acid, whereby all but the sulfides or the Vl group metals are dissolved, separating the undissolved residue from the solution, and washing the residue.

2. Method according to claim 1 in which the spent catalyst is first treated with a suitable solvent to remove adhering hydrocarbon material.

3. Method according to claim 1 in which the residue undissolved by strong hydrochloric acid is treated with a dilute mineral acid before washing.

4. Method according to claim 1 in which the digestion with strong hydrochloric acid is carried out in the presence of an oxidizing agent.

5. Method for recovering a catalytically active form of molybdenum sulfide from a spent catalyst containing the sulfides of molybdenum, zinc and magnesium, which comprises treating the spent catalyst with carbon disulfidc to remove hydrocarbon material, digesting the extracted catalyst with strong hydrochloric acid containing a small amount of an acid oxidizing agent, separating the residue from the solution and washing the residue first with a dilute mineral acid and then with water.

6. Process according to claim 5 in which the spent catalyst is digested with about 6 normal hydrochloric acid at substantially normal temperatures.

RHEA N. WATTS. 

